Strip film



Sept. 19, 1944. F. T. POWERS; 2,358,590

STRIP FILM Filed Oct. 10, 1941 ANTI-ABRAS/ON M Mum/01v V I4 cauaolamoyfo5; ADHESIVE I DYED LAYER l0 PAPER 7 W v: LEDNGTH Patented Sept. 19, 1944UNITED STATES- PATENT OFFICE Frank '1. Powers, Glen-Cove, N. Y.Application October 10, 1041, Serial-No. 414,433

. I 4 Claims. The present invention relates to novel improvements inphotoengraving and photome .chanical reproduction and more particularlyto an improved strip film and halftone process for photomechanical use.

Objects and advantages of the invention will be set forthin parthereinafter and in part will be obvious herefrom, or may belearned bypractice with the invention, the same being realized and attained bymeans of the instrumentalities and combinations pointed out in theappended claims. i

The invention consists in the novel parts, conabsorbing most of thelight shorter than 5,500

A. Thus, the only light reaching the paper base and which mightotherwise reflect from the-base is substantially completely absorbed,and substantially no light is reflected to the emulsion which might fogthe photosensitive material.

The dyed support between the base member and the emulsion layer alsopreferably absorbs muchof the light scattered by the silver halide inthe emulsion, so that both the scattered light, and the reflected lightfrom the base are greatly reduced, causing a great reduction instructions, arrangements, combinations and'im-.

provements herein shown and described.

The accompanying drawing, referred to herein and constituting a parthereof, illustrates one embodiment'of the invention, and together withthe description, serves to explain the principles of the invention.

Fig. 1 is a diagrammatic sectional view of a typical and illustrativesheet of photosensitive material in accordance with the presentinvention: and

Fig. 2 is a graphical representation of certain general characteristicsof the various materials used with the present invention.

The present invention has for its object the provision of a novel andimproved photosensitive sheet material particularly adapted forphotomechanical use where relatively high contrast and resolvingpowerare desired. A further obiectis the provision of a novel and improved inthe making of halftone negatives which comprises a photosensitive film,such as a silver halide emulsion, releasably secured to a base, such asa sheet or web of paper. Incorporated in a thin layer permanentlyaflixed'to and carrying and supporting the emulsion,is a dye whichallows the transmission of most of the light having a wavelength shorterthan 5,500 A., and ab-, sorbs most of the light of a wave length longerthan 5,500 A., while the base member is complementarily colored, as bycoating, with a dye the light of a wave length shorter than 5,500 A.,

halation, an increase in contrast and a high effective resolvingmaterial.

The photosensitive film is releasably secured to the base member orother surface, and after development, fixation and washing, thephotosensitive film may be removed from its base member and strippedonto a sheet of glass or other negative support. During the fixation andwashingoperations some of the dyestufl may be washed out of the film andwhat remains does not substantially interfere with the transmission oflight during the operation of printing the neeative on the metal. Thisprinting operation is usually carried out by a carbon or mercury vaporare using a bichromated or chromated colloid as the photosensitiveresist on the surface of the material to be etched. Furthermore, the dyewith which the support is dyed is substantially transparent to the lightwith which the copy is illuminated, as' well as to the rays whichprincipally afiect the emulsion layer, although I have found that someadvantage is obtained in using a dye which filters out certain portionsof the spectrum 0; the light used for illuminating the copy. Theinvention will be described in detail in connection with strip filmparticularly adapted for making halftone negatives using mercury vaporarcs as the source of light for the photographic and printingoperations.

As shown in Fig. l, the strip film comprises a paper base 10, the uppersurface of which is covalthough I prefer to use a dye. which absorbs allof the light from the violet to at least 5,000 A. Such a dye usually hasan orange or reddish color, and in fact, orange and red-dyes in generalare suitable, although their visual appearance is not always asufllcient test of their suitability as some may have strongtransmission bands in the 'blue' and violet.

power of the photosensitive The photosensitive fllm comprises a silverhalide-gelatine emulsion H which is orthochromatic or panchromatic andis coated on thin support layer of dyed collodion l6, dyed andpermanently attached to and in optical contact with the emulsion layerId. The dye in support I! the colored'base member M by means of a thinadhesive layer i1 so that the first three layers are retained togetherduring exposure and developing, and separate from the base member iduring the fixing or subsequent washing. Thus, the silver halideemulsion laye containing the negative becomes detached from thepaperbase member l0 and may be stripped on to a clear glass plate, withcoating it against the glass plate.

In Fig. 2 of the drawing there is showndiagrammatically the-generalrelation of the different factors entering into the specific embodimentof the invention described above. In this diagram absorption of thevarious dyestuffs, the sensitivity of the silver halide, thechromated orbichromated photosensitive resist, and the principal lines of themercury vapor arc spectrum are all plotted against wave length in asingle diagram. v

As shown, the mercury vapor arc emits light having the approximate wavelengths 3,650 A., 4,080 A., 4,360 A., 5,460 A., 5,760 A. and 5,790 A.,the vertical length of the lines indicating roughly the relativeintensities of these various wave lengths in the mercury vapor arcspectrum.

Curve 20 shows, roughly, the sensitivity of the silver halide-gelatineemulsion, such as constitutes the layer I4, and this emulsion has amaximum sensitivity at approximately 4,000 A., and a secondary maximumsensitivity at approximately 5,500 A. No data is shown below 3,200 A. aslight of the shorter wave length is not appreassaseo Y lengths scatteredby the silver halide particles.

Curve 23 illustrates generally the sensitivity curve of a coating ofchromated colloid such as is generally used in photosensitive resistsfor the printing of halftone negatives on copper, and may be consideredtypical of various cold top enamels, this sensitizing material havingits max-' imum sensitivity at approximately 3,700 A. Curve 24 is asimilar curve illustrating the sensitivity of bichromated colloids whichhave their maximum sensitivity at approximately 3,600 A.,

ciably transmitted by the various glass plates corresponding to thesecondary maximum sensitivity at 5,500 A.

Curve 22 illustrates generally the absorption spectra of the orangedyeused for the coating of the paper base III, and this dye preferablyabsorbs most of the light of a wave length shorter than 5,500A. or atleast 5,000 A.. thereby preventing reflection of any actinic raystransmitted through the emulsion layer it and dyed layers II and H a Asanxample of a dye suitable for dyeing this layer H, toluene fast orange(Schultz No. 709) may be given assuitable. a l

The generally blue or bluish-green dye with which'the support I! .isdyed and the generally orange dyewitlrwhich the coating II is dyed aresubstantially complementary in color so that any light transmittedthrough the support I! is not and it will be noticed that both thechromated.

and 'bichromated colloids may be insolubilized by the mercury vapor arelines 3650 and 4080.

In actual practice it has been found that strip film, in accordance withthe present invention,

yields negatives which have greatly increased contrast between thehalftone dots and'the intervening portions, preserve the range of tones,reproduces much flner detail and can be etched and flnished in muchshorter time than with similar negatives made on conventional strip'filmmaterial, and in many instances no re-etching, staging or hand finishingis required on the halftone photogravings. The strip film of the presentI invention also allows much wider latitude in exposure, both in thecamera and on the metal. In fact, by the use of the strip film materialof the present invention, the usual staging or finishing operations,requiring a great deal of skill and consuming a great deal of time, arealmost completely eliminated.

The exposure required for the negative in the camera is not greatlylengthened, as the bluish dyed support I! affects only the lighttransmitted by the emulsion and might be reflected by the base it tocause halation, as will be noted from curves 20 and 2| in Fig. 2.

It will also be noticed from curves 20 and 22 ofF'ig. 2 that the orangedye of coating I I almost completely absorbs any light which mightaffect the principal sensitivity of the silver halide emulsion, and suchsmall amount of reflected light as might affect the emulsion in theneighbor- .hood of 5,500 A. is absorbed by the bluish dye insupport I 5.

During the fixing and washing operations fol-- lowing the development ofthe halftone negative,

some of the bluish dye may be removed from the support I! therebyincreasing the transparency, but such dye as does remain, does notmaterially reduce the transmission of the light from the mercury vaporarc to which the photosensitive coating on the metal is sensitive, thislight lying principally between the wave lengths 3,300 and 4,200 whichis also the range of maximum transmission by the bluish dye.-

While I prefer to use an orange or reddish dye in the coating ll, it isalso possible to use the.

, aasasao the thereby enabling the operator to readily see character ofthe negative and determine when development has been completed andwhether or not the negative is of satisfactory quality.

It is not necessary, although vit is preferable, that any of the bluishdye remain in the support I! after development. Its effect is exertedprimarily during the photographic steps in the camera, but to someextent, the same eflect is also obtained during the printing of thenegative onto metal sensitized with the bichromate or other chromic acidsalt sensitizer, the sensitiaer and blue dye being complementary to eachother.

Emept as described, the operations in the production of a h on metal,may-be carried out with the present invention as with conventional stripfilm mate- 'rial, and the same developing and fixing solutions may, ingeneral, be used.- 1

The invention in itsbroader aspects is not limited to the specificelements shown and described but departures may be made therefromalftone negative and its printing r within the scope of the accompanyingclaims without departing'i'rom the principles of the invention andwithout sacrificing its chief advantages. 4 5

What I claim is:

1. A photosensitivc material for photomechan ical reproduction includinga color sensitive silver halide emulsion layer sensitive to wave lengthssubstantially longer than 5500 A., a supporting v base, an interm tivelyfast to the treating solutions, the filtering layer transmitting lighttowhich a chromic acidsalt is sensitive and absorbing most of the reatefiltering layer dyed relamainder oi the light andthe basebeing coloredical reproduction including a color sensitive silver halide emulsionlayer sensitive to wave lengths; substantially longer than 5,500 A., asupporting base, and an intermediate filtering layer of permanentlybluish dyed collodion, the filtering layer transmitting light to which achromic acid salt is sensitive and absorbing most of the remainder oithe light and the base being colored substantially complementary to thecolor of the filtering layer and a releasable layer between thefiltering layer and base.

3; A photographic negative strip film material for photomechanical useincluding a silver halide emulsion sensitized to light ofwavelengthssubstantially longerthan 5,500 A. supported on a layer colored with asubstantially fast coloring material to transmitmost of the light oiawavelength shorter'than 5,500 A. and to absorb most oi the light of awave length longer than 5,500 A.

' and emulsion are adherent for easy detachment substantiallycomplementary .to the coloroi the filtering layer and a releasable layerbetween thefilter. layer and base.

with the colored layerintermediate the emulsion andbase, said colored'base' absbrbing most or the light of a wave length shorter than 5,500A.

and said colored layer transmitting most of the light or a wave, lengthshorter than 5,500 Land absorbing most 0! the light longer than 5.5001."

A photosensitive. material for photomechan-

